Flexible sealing boots or dust covers



May 4, 1965 H. FINEMAN 3,181,376

FLEXIBLE SEALING BOOTS OR DUST COVERS Filed Sept. 4, 1962 United States Patent 9 3,381,376 FLEXIBLE SEALING BOOTS OR DUST CGVERS Harold Fineman, Birmingham, England, assignor to Girling Limited, Birmingham, England, a British company Filed Sept. 4, 1962, Ser. No. 221,037 Claims priority, application Great Britain, dept. 6, 1% 31,959/61 7 Claims. (Cl. 74-182) This invention relates to improvements in flexible sealing boots or dust covers such as are used for making a seal between relatively movable members in order to exclude dust and moisture.

For example, in order to protect the point at which an actuating rod or plunger for the piston of an hydraulic master cylinder enters the end of the cylinder, it is usual practice to employ a corrugated rubber boot or dust cover which is secured at one end to the cylinder, and at the other end to the rod or plunger, the boot expanding and contracting axially as the rod moves out of and into the cylinder.

Annularly corrugated rubber boots are expensive, but if a plane cylindrical or conical rubber boot is employed, it does not collapse smoothly when contracted in length, and tends to form folds having sharp angles at which the rubber ultimately fails.

According to our invention, a rubber boot or dust cover is combined with a former of such an outline in relation to the shape of the boot that when the boot is contracted or expanded axially, the wall of the boot rolls over the former into itself smoothly and substantially without creases or kinks.

Thus no part of the boot is over-stressed, and there is no tendency for it to fail at any particular point so that it has a long working life.

The boot and former can be of any convenient complementary shape, but in a preferred construction the boot is of substantially conical form and is employed in conjunction with an oppositely tapered conical former of which the narrow end is engaged by the narrow end of the boot.

In the accompanying drawings:

FIGURE 1 is a diagrammatic view showing the outer end of a boot in accordance with our invention, with the boot in the unstressed condition;

FIGURE 2 is a similar view showing the way in which the boot rolls on to the former;

FIGURE 3 is a side elevation in part section of a fluidpressure motor in which the control rod is fitted with a boot and former in accordance with our invention; and

FIGURE 4 is an enlarged section of the construction between the boot and the control rod shown in FIG- URE 3.

In the arrangement shown in FIGURES 1 and 2, a moulded rubber boot for sealing an axiallly movable rod has a tubular cylindrical inner portion 11 fittting closely around the rod and a conical outer portion 12 integral with the inner portion to which it is joined at its outer end by a radiused annular portion 13. A coned former 14 tapered in the opposite direction to the boot is mounted on the rod outside the boot with its smaller inner end in engagement with or closely adjacent to the outer end of the boot in the normal unstressed condition of the boot shown in FIGURE 1.

When the rod is moved axially to the left, the former moves into the outer end of the boot which rolls smoothly over the former into itself, as shown in FIGURE 2.

In the practical arrangement shown in FIGURES 3 and 4, a control rod 15 of a fiuid-pressure'motor 16 is sealed relative to the body of the motor by a moulded rubber boot 17 surrounding the rod, The inner end of dfldlfilb Fatented May 4, 1935 the boot is cylindrical, and terminates in an annular bead 18 which is received in a complementary annular channel 19 in a boss 21 on the end wall of the motor through which the rod extends, the bead being in sealing engagement with the boss. The outer end of the boot is frustoconical and leads into a radiused and inturncd annular portion 22 terminating in a head 23, the inturned portion flitting closely around the rod to which it is clamped by a circlip or spring ring 24 as shown more particularly in FIGURE 4. A coned former 25 is screwed on to the rod outside the boot with its smaller inner end just engaging or very close to the outer end of the boot in the normal unstressed condition of the boot.

When the rod 15 is moved axially into the motor, the outer end of the boot rolls over the former into itself as described above with reference to FIGURES 1 and 2.

The former may be an integral part of the rod, as shown in FIGURES 1 and 2, or it may be a separate member which is screwed on to the rod as shown in FIGURES 3 and 4, or is secured to the rod in any other convenient manner.

If it is a separate member, it may be made of metal or plastic, or any other rigid or substantially rigid material.

The term rubber used herein is intended to include natural or synthetic rubber or plastic having similar properties.

in the embodiment described above, the boot is moulded in its unstressed or extended condition. In a modification it may be moulded in its stressed or rolled condition in which case as the boot is extended axially, it is unrolled with the aid of a former of suitable shape.

I claim:

1. A device for making a seal between two relatively movable members comprising a boot of flexible material attached at one end to one of said members and at the other end to the other of said members, one of said members extending axially through said boot, a former carried by one of said members and positioned outside said boot, said boot and said former being shaped such that upon relative axial movement of the members towards one another, the former and boot move from a disengaged position into an engaged position where the boot is adapted to roll smoothly over the former and into itself.

=2. A device as claimed in claim 1, in which the former is adjustably mounted on said member.

3. A device as claimed in claim 1, in which the former is adjustably and removably mounted on said member.

4. A device for making a seal between an axially movable member and a stationary member comprising a boot of flexible material attached at one end to: said movable member and at the other end to said stationary member, one of said members extending axially through said boot, a conical fonmer carried by one or" said members and positioned outside said boot, said boot including a conical portion tapered in a direction opposite to the direction of taper of the former such that upon axial movement of the movable mem'ber towards the stationary member the conical portion of said boot is adapted to roll smoothly over the former and into itself.

5. A device for making a seal between a rod and a member relative to which the rod is axially movable comprising a boot of flexible material having a conical portion in sealing engagement at its end of smaller diameter with saidrod and at its end of larger diameter with said member, said rod extending axially through said boot and carrying a conical former positioned outside said boot, the conical portion of said boot being tapered in a direction opposite to the direction of taper of the former such that upon axial movement of the rod the conical portion of said boot is adapted to roll smoothly over the former and into itself.

6. A device as claimed in claim 5, in which the end of smaller diameter of said boot leads into a reversely curved annular portion which fits closely around and is clamped to "said rod adjacent the former at its end of smaller diameter.

7. In a fluid-pressure motor having a body member,

and a control rod axially movable with respect to the body member, a device for making a seal between the control rod and the body member comprising a moulded rub ber boot surrounding the rod and which in [the unstressed condition comprises a fTusto-co-nical portion having an'annular bead at its end of smaller diameter for attachment to the rod, said rfrusto-conical portion terminating at its end of larger diameter in a cylindrical portion having an annular bead for attachment .to said body member at its end remote from said fru sto-conical por- ,tion, a conical former carnied by said rod and positioned outside the :boot, said conical former tapered in a direction opposite to the taper of the frusto-conical portion UNITED STATES PATENTS 1,859,611 5/32 Yungl-ing 7418.2 1,904,358 4/33 Dahlberg 74l8.2 2,544,541 3/51 McCarthy et -al. 74-182 BROUGHTON G. DURHAM, Primary Examiner. 

1. A DEVICE FOR MAKING A SEAL BETWEEN TWO RELATIVELY MOVABLE MEMBERS COMPRISING A BOOT OF FLEXIBLE MATERIAL ATTACHED AT ONE END TO ONE OF SAID MEMBERS AND AT THE OTHER END TO THE OTHER OF SAID MEMBERS, ONE OF SAID MEMBERS EXTENDING AXIALLY THROUGH SAID BOOT, A FORMER CARRIED BY ONE OF SAID MEMBERS AND POSITIONED OUTSIDE SAID BOOT, SAID BOOT AND SAID FORMER BEING SHAPED SUCH THAT UPON RELATIVE AXIAL MOVEMENT OF THE MEMBERS TOWARDS ONE ANOTHER, THE FORMER AND BOOT MOVE FROM A DISENGAGED POSITION INTO AN ENGAGED POSITION WHERE THE BOOT IS ADAPTED TO ROLL SMOOTHLY OVER THE FORMER AND INTO ITSELF. 